I don't understand why the standard method is used... Am I missing something?
I see at least three advantages to the top option.
1) A 10ft rafter is a 10ft rafter. You can cut an angle at the top to meet the ridgeboard, and still have 10ft to match your 10ft sheet of roofing. The other way, you lose a few inches to make that bottom vertical. So.. a 10ft roof sheet needs a 12ft rafter, with maybe a 20" offcut...
2) You don't need to take the time to measure, mark, and make that angled offcut, multiplied by however many rafters.
3) It catches rain just fine, judging by the shed I put up a couple years ago... but sheets of snow slide over top of it, seeming much less likely to rip the gutter off the roof.
So,is there any good reason for the 'normal' way? Clue me in!
'Theoretically this level of creeping Orwellian dynamics should ramp up our awareness, but what happens instead is that each alert becomes less and less effective because we're incredibly stupid.' - Jerry Holkins
Here the water would run right over the first image, I think it's going to depend on the pitch of the roof and how much water you get in one go. Saying that our gutters are different again our fascia board is at an angle like picture 1 but the gutter is like picture 2. the difference is in the fastener.
I don't think there's a functional reason why you couldn't do the angled approach. One tactical possible reason is if you're putting metal soffit under the overhang. By cutting the tails vertical, you can attach metal fascia to it which has a 90 degree lip at the bottom. That will then support the soffit that runs horizontally over to the wall. Connecting horizontal soffit to an angled fascia could be trickier when you're building lots of houses.
As for the rain and snow thing, I've found that I need to drop my gutters significantly below the projection of the roof slope to keep the snow from ripping them off (snow curling off a metal roof). And it never seems to rain hard enough that the water shoots over the gutters, even if they're down 2" from the slope of the roof.
Also, the gutter fasteners may have a stronger support when mounted vertically. On the angle, all the force is pulling the screws or spikes out. Horizontally the fascia provides some support. Maybe